The overall objective of the proposed research is to develop an in vitro experimental model for toxicological and carcinogenesis studies using xenotransplanted-reconstituted human epithelia. Epithelial cells obtained from immediate autopsies of full term fetuses will be isolated and inoculated into deepitehlialized rat tracheas, which will be subsequently sealed, and transplanted subcutaneously into athymic nude mice. The main part of this project comprises the study of normal and carcinogen-treated xenotransplanted-reconstituted human respiratory epithelium. In an initial phase, the kinetics of repopulation of the human xenotransplanted epithelium and the revascularization of the tracheal transplants will be studied in order to ascertain the kinetics of epithelial repopulation as well as to determine the presence of an adequate blood supply. Eventual tumor development as well as other late and early changes induced by 7,12-dimethylbenz(a)anthracene will be studied sequentially during 12-18 months after initiation of exposure. A series of tumor markers of proven clinical or experimental will be studied at different timepoints using smears of tracheal secretions and tissue sections. In the initial phase the following markers will be monitored by histoenzymological and histoimmunochemical techniques: gamma-glutamyl transferase ornithine decarboxylase, carcinoembryonic antigen, ecotopic hormones, loss of blood group antigens and lectin binding. Later other markers such as hematoporphyrin binding, specific anti-lung antibodies etc. could also be investigated. In addition, the in vitro evaluation of altered growth potential of in vivo carcinogen exposed cells will be carried out. Sequential morphological changes will also be evaluated by light microscopy, histometry and transmission electron microscopy.